Process for shrinking and setting polyacrylonitrile textile filaments with specific chemical shrinking agents



United States Weston Andrew Hare, Staunton, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application March 28, 1955 Serial No. 497,439

Claims. (Cl. 8-130.1)

This invention relates to setting the'crimp in acrylonitrile polymer yarns and fibers. The invention also applies to shrinking acrylonitrile polymer yarns and fibers.

This is a continuation-in-part of my application Serial No. 462,630, filed October 15, 1954 now abandoned.

Crimp is added to filaments and fibers ofacrylonitrile polymers and copolymers to improve bulk and processability. Unless the crimp is set in a permanent manner, much of the advantage may be lost during processing. Knit wear produced from crimped filament or fiber yarns of acrylonitrile polymers and copolymers wherein the acrylonitrile content is not less than about 85% has a very desirable handle. However and especially in the case of copolymers, the loft, bulk or covering power is generally greatly diminished by hot-wet processing (such as boil-off and dyeing) of the knit structure so that the fabric acquires an open, hungry appearance. This reduction in bulk during fabric finishing is believed to be caused primarily by crimp loss occurring in the boilotf and dyeing of the knit goods. Yarns prepared from acrylonitrile homopolymer retain crimp under these hotwet treatments much better than do yarns from copolymers of acrylonitrile prepared using up to about of one or more ethylenically unsaturated compounds copolymerizable with acrylonitrile. In fact, comparison of results between knit wear of acrylonitrile homopolymer yarn and of acrylonitrile/methyl acrylate (94/6) copolymer yarn shows bulk loss in the copolymer fabric to be about 25% more than in the homopolymer fabric. Thus, while acrylonitrile homopolymer yarn knit wear is readily acceptable when properly fabricated from the right denier yarn for a given construction, 25 more yarn is needed when using only a copolymer yarn in order to produce a similar article with equal acceptability.

It has been shown that the desired loft or bulk can be retained by setting the crimp under conditions that will substantially resist removal during the hot-wet treatment used in the finishing of the knitted goods by pressure treatment of the crimped staple in a confined space with water in liquid form at 120 C. However, pressure treatment is costly and a more expedient methodof crimp setting with at least asgood results is desired.

Accordingly, an object ofthis invention is to'provide an improved process for setting the crimp, crinkle or curl in acrylonitrile polymer and copolymer filaments, fibers and yarns, without involving super-atmospheric pressures. Another object of this invention is to provide an improved process for shrinking yarns, filaments and fibers without resorting to super-atmospheric pressure conditions. These and other objects will be apparent from the description that follows.

The objects of this invention are accomplished by impregnating the crimped fibers, filaments, yarns or the like comprised of acrylonitrile polymers or copolymers .wherein the acrylonitrile content is not less than about 85% with a dilute aqueous solution heated to at least about 75 C. and containing; about 10% to about 40% of a compound selected from the group consisting of ethylene carbonate, propylene carbonate, trimethylene carbutyrolactone. The concentration of the solution will vary with the time of treatment and the eflicacy of the specific compound used. When excessive shrinkage of the fiber structure is desired, the concentration should be substantially higher than for crimp setting, e. g., two or' three times as much, and with acrylonitrile homopolymer as much as 30% or even 40% adjuvant may be contained in the treating bath which may be three or four times as much as needed for a copolymer fiber. For shrinkage, amounts of about 1% to about 40% are used. The processes are carried outat atmospheric pressure. The polymers that are used in the manufacture of the fibers used in this invention are well-known, having been described in the art in such patents as U. S. Nos.

2,404,714, 2,404,727 and 2,486,241. Thus, the polymers contain to acrylonitrile and copolymers may be derived from the polymerization of acrylonitrile with monoethylenically or diethylenically unsaturated compounds as vinyl acetate, vinyl chloride, vinylidene chloride, methyl vinyl ketone, styrene, vinylpyridines, acrylic acid and methacrylic acid or their derivatives such as their esters, ethylenesulfonates, l-propenylsulfonates, styrenesulfonates and the like. The copolymers may be comprised of two or three or more copolymerizing compounds.

To measure quantitatively the amount of retained crimp and the shrinkage factor which are given in several examples that follow, the test procedures set forth below were devised. The drawn yarn was knitted and the knitted sample about 5" x 5" was immersed in a treating solution of thisinvention, usually at or near the boil. The sample was then rinsed and reboiled in demineralized Water for ten minutes and dried at 70 C. Yarn raveled from such a sample of treated knit tubing was tested for crimp stability as follows: The raveled yarn was subject to mild tension in hot water by suspending from a loop of the yarn a weight of 17 milligrams. This weighted loop was lowered into a beaker of hot water (92 to 94 C.) and held there for five minutes. The yarn was taken from the bath and the weight removed and then the loop was reimmersed in the hot Water for one minute, after which the yarn'was oven dried at about 70 C. The number of crimps per centimeter in the dried, looped yarn were counted and are listed in the tables that follow in the columns under the heading retained crimp. Shrinkage of the knit tubingwas measured by counting the courses and the stitches per where C and S are courses and stitches per centimeter respectivelyand iand t mean initial and treated, respectively. i

The'following examples are given to further illustrate the invention without any intention of being limited thereby. Parts and percentages are by weight unless otherwise indicated.

I EXAMPLEI' I 7 A copolymer of acrylonitrile/methyl aciylate (9 4/6) was dry spun from N,N-dimethylformamidesolution to produce 330 denier- 30 filamentas-spun yarn which was hot-wet drawn 4 to produce a final yarn of about 85 denier and collected on'suitable cores. knitted from .the wet packages to a loose structure 11. x 14 courses x stitches per centimeter-and swatches of; this knitted structure were subjected for tenrninutes at 98 C. to the aqueous solutions listed in Table A below, The

Patented Jan. 20, 1959,

The yarn was results obtained following the test practice previously described and using a large excess of bath to swatch are also set forth in Table A.

Similarly, using the knit structures of Example 1, i. e., a medium type structure having 16.5 x 14.5 courses x stitches per square centimeter but otherwise the same as in the first part of this example, the following results were obtained as set forth in Table 13.

Table B Adjuvant 00110., Shrinkage Retained Percent Factor Crimp/em.

Water (at 98 O.) 0.51 7.8 Water (at 120 0.). 0.57 10. 5 Butyrolaetone 0. 53 9. 5

Thus, it is seen that 10% ethylene carbonate or 10% nitromethane at 98 C. are as eifective in setting the crimp as is water at 120 C. while butyrolactone at 10% concentration shows substantial improvement in crimp setting over water at the same temperature (98 C.). In subsequent tests, it was found that concentration of butyrolactone in water was at least as effective as water at 120 C. Similarly, about 15% and aqueous solutions of trimethylene cyclic carbonate and deltavalerolactone, respectively, are effective in setting the crimp in similar swatches of knit fabric. Other solvents and near solvents for acrylonitrile polymers were relatively ineffective even at much higher concentrations than shown above. For example, 10% solutions of sulfuric acid, calcium chloride, zinc chloride, N-acetylmorpholine, maleic anhydride, calcium thiocyanate, tetramethylene sulfone, acetonitrile and N,N-dimethyl formamide were ineffective. Even aqueous N, N-dimethylfo-rrnarnide in concentrations as high as and at C. failed to give as high a retained crimp as did water at C. or as did the treating media of this invention.

EXAMPLE II swatches which were subjected to tests as previously described with the results recorded below in Table C. tn this case, the shrinkage factor recorded is the extra shrinkage above that obtained by boiling off the fabric. The first three samples in the table were treated by padding the solution on to the fabric samples and heating in atmospheric steam, while the other samples were treated by boiling in a large excess of solution.

effective as boiling in an excess of 10% solution, showing that the fabric absorbs the adjuvant from the bath. Also, 15% ethylene carbonate padded on as a 15 aqueous solution was equivalent to boiling in an excess of a 10% solution. These data also indicate that 15 butyrolactone is about equivalent to 10% ethylene cyclic carbonate as an adjuvant while 20% butyrolactone solution was a much more effective bath for shrinking and crimp setting than was 10%. ethylene carbonate solution.

EXAMPLE III Yarn samples prepared as described in theffirst part; of Example I and in the form of small skeins were subjected to shrinkage tests with water and with ethylene carbonate with the shrinkage results and physical properties of the shrunk yarn as set forth in Table Dv below.

Table D 10% 20% Treating Solution Water Water Ethylene Ethylene Garbon- Carbonate ate Temperature, C 99 120 99 101 Percent Shrinkage 24 30 30 48 Denier 115. 5 119. 6 128.1 161. 5. Straight:

Tmlcity, g. p. d 2 78 2. 80 2. 52 1.98 El Jngation, Percent; .6 24. 3 25.3 28; 2 Loop:

Tenicity, g. p. d 2. 61 2. 49 2. i0 2.05 Elingation. Percent." 21.0 22. 2 22. 2 28. 5

20% ethylene carbonate shrunk the yarn much more than did 120 C. water and, even at the conditions that gave high shrinkage, a fair degree of yarn tenacitywas retained.

EXAMPLE IV To study the effectiveness of short times of treatment, samples of knit tubing prepared from 4X drawn yarn of acrylonitrile/methyl acrylate copolymer (94/ 6) were im-. mersed in boiling solution for five to fifteen seconds, thenrinsed in water and boiled ten minutes in water to remojte. the treating agent. The results in terms of retained crimp. per centimeter are given below in Table E.

10% solutions of ethylene carbonate or nitromethane were not effective up to fifteen seconds. increasing the concentration to 15% gives sufficient crimp settingpotential to obtain rapidsetting so that ten and fifteen T able C S01. Heat Shrinkage Retained Sample Reagent Conc., Percent On Fabric Time, Factor Crimp/cm.

- Percent Min.

1 Ethylene Carbonate 10 10 5 0.08 8. O 10.. 5 0. 15 7. G 15 5 0.17 3.0 Boiled in 801-. 10 0.22 8.0 do.. 10 0.10 8.0 do 10 0. 30 9.5 Boiled at. 15 p. s. 10 0.11 7.0

These data show that 10% ethylene carbonate on the fabric was more effective, when padded on the fabric as a 15% solution than as a 10% solution. Neither was as EXAMPLE v A 4 drawn yarn prepared from acrylonitrile homopolymer knitted into tubing and swatches thereof subjected to ten minutes treatment in the solutions and at the temperatures indicated in Table F below yielded the shrinkage and crimp setting results recorded in this table.

Table F Cone, Temp, Shrinkage Retained Adjuvant Percent C. Factor Crimp/ Water 98 0.05 5. 2

Do 120 0.05 6. 5 Ethylene Carbonate 100 0.15 6. 9 Nitromethane 98 0. 5. 4 Butyrolactone 100 0. 05 5. 7

In spite of the higher than normal concentrations of adjuvant in the treating solution, only the solution of ethylene carbonate produced greater retained crimp per centimeter than did the water treatment at 120 C. Nevertheless, the 20% solutions of nitromethane and of butyrolactone were somewhat effective and at still higher concentrations, equivalent crimp setting results are obtainable.

EXAMPLE VI EXAMPLE VII A batt was made from 3-denier, 3-inch acrylonitrile/ methyl acrylate (94/6) copoiymer fiber by carding the fibers on to a crosser-lapper. The batt was needle-punched times on a standard Hunter Machine Co. plate-type 40 10 weighed 9.1 ounces per square yard. The batt was immersed in a boiling solution of 25% ethylene carbonate in water. Instantaneous shrinkage took place to the extent of 32% in area. The shrunken batt was boiled off in water for fifteen minutes to remove the excess ethylene 15 carbonate, after which it was dried and pressed. The finished felt bad a weight of 13.4 ounces per square yard and is useful as a wicking material.

EXAMPLE IX 20 A batt of 3-denier, 2-inch fiber made from acrylonitrile/methyl acrylate (94/6) copolymer was needlepunched 25 times with 7-hour etched 15 x 18 x 25 x 3% needles. Samples were then immersed in 20% by volume mixtures of propylene carbonate and water under the 25 following conditions with" the listed resultant shrinkagea,

.Talile G Percent Area Shrinkage Temp.

Remarks 71 Shrinkage instantaneous. 67 Shrinkage requires 15-80 seconds. 10 Shrinkage requires several minutes.

5 EXAMPLE X As shown in Example IX, effective shrinkage can be attained at 82 C., 67% area shrinkage resulting in that experiment. The influence of temperature on the efliciency of ethylene carbonate and propylene carbonate may beyseen in the following table:

Table H Ethylene Carbonate fiolution Propylene Carbonate Solution 26% Cone. 28%0onc. 22% Gone. 24% Cone. (by weight) 7 g (by-weight) (by weight) (by weight) Area Area Area Area C. Shrmk- C. Shrink- C. Shrink- C. Shrinkf percent percent percent percent needle-loom at a rotational speed of 250 R. P. M. and a linear speed of yards per hour, using number 15 x 18 x 25 x 3 /2 regular barb felting needles which had been etched in 37% hydrochloric acid for seven hours.

' After needle-punching, the batt weighed 4.0 ounces per square yard. The batt was immersed in a boiling solution of 25.9% ethylene cyclic carbonate in water. Instantaneous shrinkage of the batt took place to the'extent of 74% in area. The shrunken batt was then boiled off in; water for fifteen minutes to remove the excess ethylene carbonate, after which it was dried and pressed.

yard and would be useful as a filtration fabric.

7 EXAMPLE VIII A batt was made from B-denier, Z-inch fiber prepared 70 Thefinished felt had a weight of 15.4 ounces per square The efiect of concentration is noted in Table I below:

I .Table l EFFICACY or. SOLUTION vs. CONCENTRATIONAT 100 o As canbeseen from Tables I and K relating to propylene carbonate and ethylene carbonate, respectively, the efficacy. ofgthe shrinking agentdrops ed with increasing length of time the solution is held at this elevated temperature. In all cases, the shrinkage indicated occurred within a few seconds.

EFFICACY OF ETHYLENglfilgRBoNATE SOLUTION VS 26% at 100 C. 28% at 90 C.

Percent Area Shrinkage Percent Area Shrinkage Time, Minutes Time, Minutes From the result shown above, it is noted creasing the temperature or the concentration an increase in shrinkage is attained. However, lengthening the time over which the hot solution is maintained leads to a loss in effectiveness. This is attributed to loss of shrinking agent through degradation and the effect is much more pronounced at 100 C. than at 90 C. In practice, it may.

well be desirable to operate at lower solution temperatures, such as 8090 C., to attain a more uniform. shrinking effect in batt to batt over a period of'time.

Although the invention has reference to crimp setting yarn in the form of knitted structures, it should be understood that these illustrations are in the nature or reproducible tests to assess quantitatively the efiicacy of the treatment. Fibers, filaments, yarns and tows may be crimped and crimp set in much the same stage of manufacture. In some cases, a tow of filaments may be crimped and thercrimp setting may not take place until the crimped filaments have been converted into staple. So, too, excessive shrinkage may be effected at any time and'atthe stage of manufacture Where it is needed. Applications of the shrinking agents may be made early in the manufacturing process prior to winding and/or fabricating, or they may be delayed and used in the course of converting fibers, filaments, yarns or the like into fabric structures For example, the shrinking agents may be applied during a felting process to bring about better felting properties, or they may be applied to felts or formed fabrics, woven or nonwoven, to prevent laddering, or tostifien, or to full them. The process may be used with blends such as acrylonitrile polymers or copolymers with wool, cotton, rayon, etc.

As is apparent from the data given above, the con centratiOn of adjuvant in the aqueous treating solution may vary-widely, depending on the form of or specific that by inbeen largely described by use intended for the treated fibers, filaments or yarns; i. e., whether crimp setting or excessive shrinkage is primarily desired. Also, acrylonitrile homopolymer structures require more drastic treatment than do copolyrner structures containing 85% to 99% acrylonitrile. The concentration will, of course, be governed by the temperature of the treating bath, the method of its application, the relative eificacy of the specific agent and the length of time the treating solution is maintained at the elevated temperature. In some cases, concentrations as high as 30% to or even more may be used. Let, as little as 10% or slightly less may prove entirely satisfactory, as for example in the case of ethylene carbonate. Generally, temperatures near the atmospheric boiling point of the solution are preferred, for instance 90 to 100 C. or higher, but frequently with the better agents, acceptable results can be secured at temperatures as low as about C. Instead of placing the fibers to be treated in the liquid treating agents, a spray or vapor of the solutions at the said temperatures may be directed against the fibers. The simplest method is the immersion technique and this is preferred. The time involved may be from one second to about twenty minutes, the time being usually ten seconds or longer. Generally there is no need to carry out the treatment for more than twenty minutes and long treatments especially at the higher temperatures are to be avoided, unless some other treatment is being simultaneously effected and the lower shrinkage is satisfactory.

In the manufacture of felts from synthetic filaments and fibers, the key to success is a higher order of retractability. The instant invention is eminently suited to the production of very high shrinking fibers and filaments. Accordingly, the invention is readily adaptable for use in the process of forming needled felt described in Lauterbach application Serial No. 312,067, filed September 29, 1952, .now abandoned, as well as in other felting processes.

For best results, the treated material should be rinsed and preferably boiled in water to remove the adjuvant. omplete removal of the adjuvant from the fiber structure after it has effectively set the crimp or shrunk the fiber may not always be accomplished because of the selective absorption of some of these treating agents within the acrylonitrile polymer structure. Generally, very iittle or no adjuvant remains.

This invention enables the retention of crimp, imparted to fibers and filaments soon after drawing, through numerous processing steps, such as carding, combing, drafting, spinning, winding and various fabricating steps. Not only does the setting of the crimp greatly improve loft or bulk in the final structures, but it enhances processability, with the production of higher quality end prod- ..ucts. Because the crimp can be set effectively at atmos- 'age Whenever it is desired pheric pressure, the cost of processing is greatly reduced.

Also, it is a simple matter to bring about excessive shrinkand without resorting to expensive pressure methods. It is possible to obtain good shrinkage using nitric or formic acid. For example, the use of a 3l% by weight aqueous solution of nitric acid and 60% by weight aqueous solution of formic acid led to area shrinkages on felt of 7.3 X and 7.6 respectively. However, such materials are corrosive and difii- -cult to handle and must be completely removed from the The agents of this invention I treated fibrous material. are non-corrosive and are handled with ease in conventional apparatus and small residues of the agent in the finished articles can be tolerated.

Any departure from the above description which conforms to the present invention is intended to be included within the claims.

I claim:

i. A process for shrinking and setting filamentary textile material inherently capable thereof made from a polymer obtained by polymerizing at least acrylonitrile and; up to 15% of ethylenically unsaturated monomer copolymerizable with the acrylonitrile, which comprises contacting the said textile material without dissolving it with an aqueous solution at a temperature of from about 75 C. to its boiling point at atmospheric pressure for at least one second until shrinkage takes place, said aqueous solution containing from about 10% to about 40% of a compound selected from the group consisting of ethylene carbonate, propylene carbonate, tri-methylene carbonate, nitromethane, delta-valerolactone and gammabutyrolactone.

2. The process of claim 1 in which the said polymer is a homopolymer of acrylonitrile.

3. The process of claim 1 in which the said compound in solution is ethylene carbonate.

4. The process of claim 1 in which the said compound in solution is propylene carbonate.

5. The process of claim 1 in which the said compound 'in solution is nitromethane.

6. The process of claim 1 in which the said contacting is from five seconds to twenty minutes.

7. The process of claim 1 in which the said filamentary textile material is mechanically precrimped.

8. The process of claim 1 in which the said polymer is a copolymer.

9. The process of claim 8 in which the copolymer is one of acrylonitrile and up to 15% of an ethylenically unsaturated monomer.

10. The process of claim 9 in which the copolymer is one of acrylonitrile and methyl acrylate.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,113 Hardy Oct. 8, 1940 2,249,756 Finzel July 22, 1941 2,716,586 Terpay Aug. 30, 1955 2,730,479 Gibson Jan. 10, 1956 FOREIGN PATENTS 544,821 Great Britain Apr. 29, 1942 883,764 France Mar. 29, 1943 896,083 France Apr. 17, 1944 OTHER REFERENCES Textile Research Journal, July 1954, pp. 597 and 603. 

1. A PROCESS FOR SHRINKING AND SETTING FILAMENTARY TEXTILE MATERIAL INHERENTLY CAPABLE THEREOF MADE FROM A POLYMER OBTAINED BY POLYMERIZING AT LEAST 85% ACRYLONITRILE AND UP TO 15% OF ETHYLENICALLY UNSATURATED MONOMER COPOLYMERIZABLE WITH THE ACRYLONITIRILE CONTACTING THE SAID TEXTILE MATERIAL WITHOUT DISSOLVING IT WITH AN AQUEOUS SOLUTION AT A TEMPERATURE OF FROM ABOUT 75*C. TO ITS BOILING POINT AT ATMOSPHERIC PRESSURE FOR AT LEAST ONE SECOND UNTIL SHRINKAGE TAKES PLACE, SAID AQUEOUS SOLUTION CONTAINING FROM ABOUT 10% TO ABOUT 40% OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ETHYLENE CARBONATE, PROPYLENE CARBONATE, TRI-METHYLENE CARBONATE, NITROMETHANE, DELTA-VALEROLACTONE AND GAMMABUTYROLACTONE. 